IEAv Institute Estudos Avancados

São José dos Campos, Brazil

IEAv Institute Estudos Avancados

São José dos Campos, Brazil
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Reis A.G.D.,Paulista University | Reis A.G.D.,Brazilian Nuclear Energy Research Institute (IPEN) | Reis D.A.P.,Federal University of São Paulo | Reis D.A.P.,Brazilian Technological Institute of Aeronautics | And 6 more authors.
Defect and Diffusion Forum | Year: 2016

An in situ high-temperature X-ray diffraction (HTXRD) study in maraging 300 steel was carried out to study the martensite to austenite transformation and effect of time of exposure in the austenite reversion below austenite start temperature. Solution annealed materials were subjected to controlled heating-holding cycles. The first sample was heated at a rate of 10°C/min from room temperature to 800°C, showing that the microstructure is completely martensitic (α110) until 600°C. From 650°C until 800°C, the microstructure is gradually changing from martensitic to austenitic, showed by the increasing peaks of λ111 and reducing peaks of α110. At 800°C the microstructure is completely austenitic (λ111). Another sample was heated at 10°C/min from room temperature to 600°C and held for 4 hours. At 600°C, at 0 h time of exposure, only a martensitic peak was observed. An austenite peak can be observed after some time of exposure at this temperature. The volume fraction of austenite increased with increasing time of exposure at 600°C, reaching 50/50 volume fraction after 4 hours of exposure. XRD diffraction patterns for the same sample that was held for 4 hours at 600°C and then cooled down in air to room temperature showed the same intensity of austenite and martensitic peaks found in situ at 600°C for 4 hours (retained austenite), with the volume fraction of 50/50 of austenite and martensite phases. The HTXRD technique can be used to identify and quantify martensite to austenite transformation and austenite retention. © 2016 Trans Tech Publications, Switzerland.

De Faria A.C.A.,IEAv Institute Estudos Avancados | Silva P.R.,Federal University of Minas Gerais
Canadian Journal of Physics | Year: 2016

In this work, we first use Thompson's renormalization group method to treat QCD-vacuum behavior close to the regime of asymptotic freedom. The QCD-vacuum behaves effectively like a "paramagnetic system" of a classical theory in the sense that virtual color charges (gluons) emerge in it as a spin effect of a paramagnetic material when a magnetic field aligns their microscopic magnetic dipoles. Making a classical analogy with the paramagnetism of Landau's theory, we are able to introduce a kind of Landau effective action without temperature and phase transition for just representing QCD-vacuum behavior at higher energies as being magnetization of a paramagnetic material in the presence of a magnetic field H. This reasoning allows us to use Thompson's heuristic approach to obtain an "effective susceptibility" (χ > 0) of the QCD-vacuum. It depends on the logarithm of the energy scale u to investigate hadronic matter. Consequently, we are able to get an "effective magnetic permeability" (μ > 1) of such a "paramagnetic vacuum". As the QCD-vacuum must obey Lorentz invariance, the attainment of μ > 1 must simply require that the "effective electrical permittivity" is ϵ < 1 in such a way that μϵ = 1 (c2 = 1). This leads to the anti-screening effect, where the asymptotic freedom takes place. On the other hand, quarks confinement, a subject which is not treatable by perturbative calculations, is worked by the present approach. We apply the method to study this issue for obtaining the string constant, which is in agreement with the experiments. © 2016 Published by NRC Research Press.

Castro R.M.,IEAv Institute Estudos Avancados | Castro R.M.,University of Taubaté | Vanin V.R.,University of Sao Paulo | Pascholati P.R.,University of Sao Paulo | Maidana N.L.,University of Sao Paulo
AIP Conference Proceedings | Year: 2011

The intensities of weak gamma-ray transitions in the 152Sm level scheme from 152Eu decay measured in two gamma-ray coincidence experiments are compared; almost 40 new transitions with intensities around 10 -5 gamma-rays per decay and 6 new levels were observed. One of the experiments was reanalysed to confirm some findings and this new data were included in this comparison. Despite some discrepancies, the obtained decay data are in general agreement. The measured energies form a consistent data set but the intensities not, suggesting that the uncertainties are underestimated by a factor of 2. © 2011 American Institute of Physics.

Da Silveira C.R.,Federal University of Pará | Costa J.W.A.,Federal University of Pará | Giraldi M.T.R.,Military Institute of Engineering of Rio de Janeiro | Franco M.A.R.,IEAv Institute Estudos Avancados | Jorge P.A.S.,INESC Porto
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2013

This work presents numerical results related to an in-line Mach-Zehnder interferometer used as a refractive index sensor. The in-line Mach-Zehnder is based on abrupt tapers in standard single mode optical fiber. Numerical simulations were carried out using commercial software based on Beam Propagation Method in order to analyze the sensitivity response in terms of wavelength shift when this sensor is bent at certain radii of curvature. We realized that application of bending in the In-line Mach-Zehnder interferometer enhanced considerably the sensitivity of this sensor to the external refractive index. The best result was achieved for a radius of curvature of 10 mm (500 nm/RIU for the refractive index range of 1.33 to 1.41) improving the sensitivity about eight times in comparison with the case with no bent. © 2013 SPIE.

Pillat V.G.,University of Paraíba Valley | Pillat V.G.,National Institute for Space Research | Guimaraes L.N.F.,National Institute for Space Research | Guimaraes L.N.F.,IEAv Institute Estudos Avancados | And 2 more authors.
Computers and Geosciences | Year: 2013

The purpose of this work is to present a new computational tool for ionogram generated with a Canadian Advanced Digital Ionosonde (CADI). This new tool uses the fuzzy relation paradigm to identify the F trace and from this form extract the parameters foF2, h'F, and hpF2. The tool was very extensively tested with ionosondes that operate at low latitudes and near the equatorial region. The ionograms used in this work were recorded at São José dos Campos (23.2° S, 45.9° W; dip latitude 17.6° S) and Palmas (10.2° S, 48.2° W; dip latitude 5.5° S). These automatically extracted ionospheric parameters were compared with those obtained manually and a good agreement was found. The developed tool will greatly expedite and standardize ionogram processing. Therefore, this new tool will facilitate exchange of information among many groups that operate ionosondes of the CADI type, and will be very helpful for space weather purposes. © 2012 Elsevier Ltd.

Fogagnolo J.B.,University of Campinas | Rodrigues A.V.,University of Campinas | Lima M.S.F.,IEAv Institute Estudos Avancados | Amigo V.,Polytechnic University of Valencia | Caram R.,University of Campinas
Scripta Materialia | Year: 2013

A novel proposal is presented to increase the fatigue strength of titanium parts by applying a less rigid coating, which is expected to lower the tensile stresses at the surface and delay the onset of fatigue cracking. Niobium was introduced into the surface layer by laser surface alloying and, depending on the process parameters, β and α″ phases were obtained, resulting in a reduction of approximately 30% in Young's modulus and a more than 100% increase in hardness. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Pillat V.G.,University of Paraíba Valley | Fagundes P.R.,University of Paraíba Valley | Guimaraes L.N.F.,IEAv Institute Estudos Avancados
Journal of Atmospheric and Solar-Terrestrial Physics | Year: 2015

F-region large-scale irregularities, also called plasma bubbles, are one of the most interesting equatorial ionospheric phenomena. These irregularities are generated in the equatorial region and afterwards extend to lower latitudes. They are one of the important topics of investigation in equatorial ionosphere electrodynamics and, therefore, are subject to intense theoretical and experimental research. The ionosonde is the most used scientific equipment to study the ionosphere and the F-region. With advancement of digital ionosonde, it is now possible to carry out an ionospheric sounding with a cadence of 5. min or even with 1-minute cadence. To analyse a large amount of ionograms, more sophisticated tools are needed. Thus, development of algorithms to identify and analyse different aspects of ionograms has become very important to space science researchers. Multiple echoes recorded on ionograms are the signature of these irregularities in the ionograms, usually called Spread-F. Spread-F is classified into three types: range, frequency, and mixed. Thus, automatic identification of Spread-F is important in ionospheric studies, because studies usually involve the analysis and interpretation of large numbers of ionograms. The main objective of this paper is to present a new computational tool, based on fuzzy relation, designed to automatically identify the occurrence of Spread-F in ionograms. The test was conducted in ionograms recorded in the Brazilian sector (São José dos Campos (23.2°S, 45.9°W, dip latitude 17.6°S-low latitude) and Palmas (10.2°S, 48.2°W, dip latitude 5.5°S-near the magnetic equatorial)). The automatic identification of Spread-F occurrence was compared with those obtained manually and good agreement was found. © 2015 Elsevier Ltd.

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